The Mayaguez incident took place between the Kingdom of Cambodia and the United States from May 12–15, 1975, less than a month after the Khmer Rouge took control of the capital Phnom Penh ousting the U.S. backed Khmer Republic. It was the last official battle of the Vietnam War. The names of the Americans killed, as well as those of three U.S. Marines who were left behind on the island of Koh Tang after the battle and were subsequently executed by the Khmer Rouge, are the last names on the Vietnam Veterans Memorial. The merchant ship's crew, whose seizure at sea had prompted the U.S. attack, had been released in good health, unknown to the U.S. Marines or the U.S. command of the operation before they attacked. Nevertheless, the Marines boarded and recaptured the ship anchored offshore a Cambodian island, finding it empty.[1] It was the only known engagement between U.S. ground forces and the Khmer Rouge.

The crisis began on the afternoon of May 12, 1975, as the American container shipSS Mayaguez, owned by Sea-Land Service Inc., passed nearby Poulo Wai island en route to Sattahip, Thailand, in waters claimed as 12 nautical miles of territorial waters by Cambodia. The U.S. did not recognize 12 nautical miles territorial waters claims at that time, recognizing only 3 nautical miles, and characterised the location as international sea lanes on the high seas.[2]:104,121-125 U.S. military reports state that the seizure took place 6 nautical miles off the island,[2]:124 but the crew brought evidence in a later legal action that Mayaguez had sailed about two nautical miles off Poulo Wai and was not flying a flag.[3]

At 14:18, a Khmer Rouge naval forces "Swift Boat" was sighted approaching the Mayaguez.[1]:26 The Khmer Rouge fired across the bow of the Mayaguez and when Captain Charles T. Miller ordered the engine room to slow down to maneuvering speed to avoid the machine-gun fire, the Khmer Rouge then fired a rocket-propelled grenade across the bow of the ship. Captain Miller ordered the transmission of an SOS and then stopped the ship.[1]:27 Seven Khmer Rouge soldiers boarded the Mayaguez and their leader, Battalion Commander Sa Mean, pointed at a map indicating that the ship should proceed to the east of Poulo Wai.[1]:29 One of the crew members broadcast a Mayday which was picked up by an Australian vessel.[1]:30-31 The Mayaguez arrived off Poulo Wai at approximately 16:00 and a further 20 Khmer Rouge boarded the vessel. Sa Mean indicated that the Mayaguez should proceed to Ream on the Cambodian mainland, but Captain Miller showed that the ship's radar was not working and mimed the ship hitting rocks and sinking. Sa Mean radioed his superiors and was apparently instructed to stay at Poulo Wai, dropping anchor at 16:55.[1]:31-32

The Mayaguez was carrying 107 containers of routine cargo, 77 containers of government and military cargo, and 90 empty containers, all insured for $5 million.[2]:47 The Khmer Rouge never inspected the containers, and exact contents have not been disclosed, but the Mayaguez had loaded containers from the U.S. Embassy in Saigon nine days before the fall of Saigon. The captain had a U.S. government envelope only to be opened in special circumstances, which he destroyed.[3]

U.S. President Gerald Ford was informed of the seizure of the Mayaguez at his morning briefing with his deputy assistant for national security affairs, Brent Scowcroft.[1]:34 At 12:05 EDT (21:05 Cambodia), a meeting of the National Security Council (NSC) was convened to discuss the situation. Meanwhile the NMCC ordered Admiral Noel Gayler, Commander in Chief, United States Pacific Command (CINCPAC), to launch reconnaissance aircraft to locate the Mayaguez.[1]:35 The members of the NSC were determined to end the crisis decisively, believing that the fall of South Vietnam less than two weeks before and the forced withdrawal of the United States from Cambodia (Operation Eagle Pull) and South Vietnam (Operation Frequent Wind) had severely damaged the U.S.'s reputation. They also wished to avoid comparisons to the Pueblo incident of 1968, where the failure to promptly use military force to halt the hijacking of a US intelligence ship by North Korea led to an eleven-month hostage situation. It was determined that keeping the Mayaguez and its crew away from the Cambodian mainland was essential.[1]:36-39 As the United States had no diplomatic contact with the Khmer Rouge regime in Cambodia, President Ford instructed Secretary of State Henry Kissinger to urge the People's Republic of China to persuade the Khmer Rouge to release the Mayaguez and its crew.[1]:39

Following the NSC meeting the White House issued a press release stating that President Ford considered the seizure an act of "piracy", though this claim did not have foundation in maritime law.[2] Secretary of Defense, James R. Schlesinger ordered the military to locate the Mayaguez and prevent its movement to the Cambodian mainland, employing munitions (including tear gas and sea mines) if necessary.[1]:40 Secretary of State Kissinger sent a message to the Chinese Liaison Office in Washington demanding the immediate release of the Mayaguez and its crew, but the chief of the Liaison Office refused to accept the note. Kissinger then instructed George H. W. Bush, then head of the U.S. Liaison Office in Beijing, to deliver the note to the Chinese Foreign Ministry and to pass on an oral message that "The Government of the United States demands the immediate release of the vessel and of the full crew. If that release does not immediately take place, the authorities in Phnom Penh will be responsible for the consequences."[1]:40

On the early morning of May 13, the P-3 Orions identified large radar returns near Poulo Wai and dropped flares on the suspected location of the Mayaguez provoking Khmer Rouge gunfire. Low on fuel, the two Orions returned to base and were replaced with another Orion from Patrol Squadron 17. At 08:16 local time the Orion made a low pass over Poulo Wai positively identifying the Mayaguez and again drawing Khmer Rouge gunfire.[1]:50-51

Shortly after the Orion made its low pass the Khmer Rouge leader, Sa Mean, ordered Captain Miller to get the Mayaguez under way. At 08:45 the Mayaguez set off towards the northeast following one of the Swift Boats.[1]:53 The Orion continued to track the Mayaguez as it left Poulo Wai. Once the location of the Mayaguez was identified, Admiral Gayler ordered the commander of the Seventh Air Force, Lieutenant General John J. Burns, at Korat Royal Thai Air Force Base, to move combat aircraft to the area.[1]:54 At 13:00 two unarmed F-111 fighter-bombers diverted from a training mission began making low-level high-speed passes by the Mayaguez. Once the F-111s had left, Sa Mean ordered Captain Miller to follow the swift boats around Koh Tang and drop anchor approximately 1.5 km north of the island.[1]:54-55 Two F-4 Phantoms soon arrived over the Mayaguez and began firing their 20 mm cannon into the water in front of the ship. The F-4s were followed by A-7Ds and more F-111s which continued to fire into the sea in front of and behind the ship indicating that no further movement should be attempted.[1]:55-56

At 16:15 the Khmer Rouge ordered the Mayaguez crew onto two fishing boats which then took them closer to the shore of Koh Tang.[1]:56-58

The Coral Sea, the Holt and the Wilson were all scheduled to arrive on station by 15 May, but none of these ships carried any troops.[1]:61 The USS Hancock carried a Marine contingent but could not arrive on station until 16 May, while the USS Okinawa also carried Marines but could not arrive until 18 May.[1]:61-62

III Marine Amphibious Force (III MAF) assigned Task Force 79.9 with recovering the Mayaguez and designated D Company 1/4 Marines in the Philippines as the unit that would actually retake the Mayaguez, but General Burns wanted additional force and orders were sent to the 3d Marine Division on Okinawa. 1st Battalion, 9th Marines (BLT 1/9) was then on alert as the primary "air contingency" reaction force, but most of BLT 1/9, were ending their tours of duty and were not subject to further extension of their tours except in the case of emergency. III MAF requested the extension of BLT 1/9's tour but this was refused.[1]:622nd Battalion, 9th Marines (BLT 2/9) (commanded by Lieutenant Colonel Randall W. Austin), was then in a training exercise on Okinawa and it received orders on the night of 13 May to return to camp and prepare for departure by air at dawn on 14 May.[1]:63-65 On the morning of 14 May BLT 2/9 boarded Air Force C-141s at Kadena Air Base to fly to Thailand.[1]:66 The 9th Marine Regiment had been the first U.S. ground combat force committed to the Vietnam War in 1965, but in May 1975 only a few of the officers and NCOs from BLT 2/9 had seen combat in Vietnam.[1]:65-66

Nine USAFHH-53Jolly Green helicopters of the 40th Aerospace Rescue and Recovery Squadron and 10 CH-53Knifes of the 21st Special Operations Squadron were stationed at Nakhon Phanom in Thailand for the rescue operation.[4]:239 There were differences between the two types which would become relevant during the battle: the HH-53 was air-refuelable, had 450-gallon foam-filled (i.e., self-sealing) tip tanks, a tail minigun with armor plating, and two waist miniguns. The CH-53 was not air-refuelable, but had 650-gallon foamless tip tanks and two miniguns, although no tail gun. Thus, the HH-53's fuel tanks were less vulnerable to ground fire and with its refueling capability, could remain in the battle area indefinitely as long as it had access to an aerial tanker.[4]:245

On May 13, General Burns and his Seventh Air Force staff developed a contingency plan to retake the Mayaguez using an assault force composed of men of the Air Force 56th Security Police Squadron. 75 volunteers from the 56th would be dropped onto the containers on the decks of the Mayaguez on the morning of 14 May. In preparation for this assault five HH-53s and seven CH-53s were ordered to proceed to U-Tapao Royal Thai Navy Airfield for staging.[1]:76-77 At approximately 21:30, one of the 21st SOS CH-53s (68-10933, call sign Knife 13) crashed en route to U Tapao, killing 18 security police and its five-man crew.[4]:240

These 23 U.S. airmen were killed when their helicopter crashed due to a mechanical failure

President Ford chaired an NSC meeting at 10:22 EDT (21:22 Cambodia), where the Air Force rescue plan was cancelled due to the loss of Knife 13 and the fact that the containers on the Mayaguez could not bear the weight of the helicopters while rappelling men down would expose them to gunfire.[1]:79 It was decided that it was necessary to wait for the Navy ships to arrive off Koh Tang and for the Marines to assemble in Thailand before a rescue attempt would be mounted. President Ford ordered the Air Force to stop any Cambodian boats moving between Koh Tang and the mainland.[1]:80

Early on the morning of May 14, the Khmer Rouge loaded the Mayaguez crew onto one of the fishing boats and they left Koh Tang following two of the swift boats on a heading for Kampong Som.[1]:91 Two F-111s swept past the fishing boat, followed by a pair of F-4s and a pair of A-7s, which began firing in front of the swift boats and then directly at the swift boats, causing one of them to turn back to Koh Tang. The jets were then joined by an AC-130H Spectre gunship from the 388th Tactical Fighter Wing which proceeded to engage the second swift boat with its cannons.[1]:92 An A-7D then sprayed the Swift boat with its 20 mm cannon, sinking it.[1]:96 The fighters then came at the fishing boat dropping bombs and firing their cannon into the water in front of it and spraying the boat with shrapnel.[1]:92 The fighter crews then reported back that 30 to 40 Caucasians had been seen on board the fishing boat.[1]:97

In Washington President Ford convened another NSC meeting at 22:30 EDT (09:30 14 May Cambodia).[1]:97 A communication link had been established between the White House, Seventh Air Force at Nakhon Phanom, CINCPAC in Hawaii and the aircraft orbiting above Koh Tang allowing for near real-time communications.[1]:95-96 The orbiting fighters reported that they could try to shoot the rudder off the fishing boat to stop its progress to Kampong Som, but the NSC decided that the risk of killing the Mayaguez crew was too great. At 23:00 EDT (10:00 Cambodia) President Ford ordered that only riot-control agents should be dropped on or near the fishing boat, while all patrol boats should be sunk.[1]:97-99

The NSC meeting continued to consider the appropriate course to resolve the crisis. It was informed that the Chinese Foreign Ministry in Beijing had refused to pass on the American note intended for the Khmer Rouge, but George Bush reported that they had read the note and that it might have been relayed to the Khmer Rouge.[1]:99 With a diplomatic solution appearing unlikely, General David Jones, acting Chairman of the Joint Chiefs of Staff, presented the NSC with a range of military options. Rescue planning was complicated by the uncertainty surrounding the location of the Mayaguez crew. It was believed that some were still on the ship, some on Koh Tang and others were on the fishing boat bound for Kampong Som. The NSC decided to proceed with a simultaneous attack by Marines to retake the Mayaguez and attack Koh Tang, together with attacking Cambodian shipping and bombing mainland targets.[1]:100

At 10:10, despite having been hit by tear gas, the fishing boat arrived at Kampong Som. The Khmer Rouge commander at Kampong Som, apparently fearing attack by the Americans, refused to accept responsibility for the Mayaguez crew and so the fishing boat moved further down the coast, dropping anchor off the island of Koh Rong Sanloem. The orbiting fighters lost track of the fishing boat once it entered the port at Kampong Som, and so this was the location transmitted up the chain of command.[1]:104-109 At 11:29, U.S. aircraft sank another patrol boat and damaged another four.[1]:337

1/4 Marines had arrived at U-Tapao from the Philippines at 05:45 on May 14 and had been waiting on standby for a helicopter assault on the Mayaguez, but as the news of the arrival of the fishing boat at Kampong Som came in the helicopter assault was cancelled.[1]:111-112 At 14:00 BLT 1/9 began arriving at U-Tapao.[1]:112

On the afternoon of 14 May, General Burns received the order to proceed with a simultaneous assault on Koh Tang and the Mayaguez timed to begin just before sunrise (05:42) on 15 May.[1]:112 D Company 1/4 Marines would retake the Mayaguez while BLT 1/9 Marines would rescue the crew on Koh Tang.[1]:113 With minimal intelligence available regarding the geography of Koh Tang, the commander of BLT 2/9 and his staff took off in a U-21 to make an aerial reconnaissance of the island. Arriving over Koh Tang at 16:00, they were prevented from closely approaching the island in order not to compromise the secrecy of the mission or draw ground fire, but they determined that the island was so covered in jungle that the only two viable landing zones available were beaches on the west and east shores of the northern portion of Koh Tang.[1]:114

At 21:00 the rescue plan was finalized. 600 Marines from BLT 2/9 — composed of Golf and Echo Companies — were assigned to conduct a combat assault in five CH-53 Knifes and three HH-53 Jolly Greens to seize and hold Koh Tang.[4]:245 Two helicopters would make a diversionary assault on the West Beach, while six helicopters would make the main assault on the wider East Beach. The East Beach force would move to the nearby compound where the Mayaguez crew was believed to be held and then move across and link up with the West Beach force. Two more waves of helicopters would be required to deploy all of BLT 2/9 to Koh Tang. The flight from U-Tapao to Koh Tang was a four-hour round trip. It was estimated that only 20-30 Khmer Rouge were on Koh Tang; the information regarding the heavy anti-aircraft fire coming from Koh Tang and the number of gunboats present was not passed on to the Marines.[1]:120-121 A unit of 57 Marines from Delta Company, 1/4 Marines together with volunteers from Military Sealift Command to get the Mayaguez under way, an explosive ordnance disposal team and a Cambodian linguist would be transferred by three HH-53 Jolly Greens to the Holt which was scheduled to arrive on station at dawn for a ship-to-ship boarding of the Mayaguez one hour after the assault on Koh Tang began.[1]:122 Two additional CH-53s (because of their superior firepower, all the HH-53s were used for troop lift) were tasked as Combat Search and Rescue helicopters, supported by an HC-130P "King" command-and-control aircraft of the 56th Rescue Squadron.

The Wilson was assigned to support the Koh Tang operation, and, after retaking the Mayaguez, the Holt would be deployed in a blocking position between Koh Tang and the Cambodian mainland with the mission of intercepting and engaging any Khmer reaction forces. Navy aircraft from the Coral Sea were given the mission of striking targets on the Cambodian mainland to prevent interference with the rescue.

At 15:52 EDT (02:52 15 May Cambodia), President Ford convened the fourth and final NSC meeting regarding the Mayaguez. General Jones briefed the NSC on the assault plan and plans for strikes by Guam-based B-52s on the port facilities at Kampong Som and the naval base at Ream. Concerned that the use of B-52s might be excessive, President Ford limited the bombing to attacks by carrier-based aircraft commencing at 07:45 (Cambodia) and gave the go-ahead to the rescue plan.[1]:123-124

Unknown to the Americans then converging on Koh Tang, none of the Mayaguez crew were on the island and it was heavily defended by over 100 Khmer Rouge. The Khmer Rouge defenses on Koh Tang were intended to counter the Vietnamese, not the Americans. Following the Fall of Saigon, the Vietnam People's Army moved quickly to take control of a number of islands formerly controlled by South Vietnam and other islands contested between Vietnam and Cambodia. The Khmer Rouge commander of Kampong Som District, Em Son, was also given responsibility for securing Koh Tang and on 1 May he took a force of 100 men to Koh Tang to defend the island against attack by the Vietnamese. Sa Mean was given responsibility for the defense of Poulo Wai.[1]:141

On the East Beach two heavy machine guns had been dug in at each end of the beach and fortified firing positions had been built every 20 metres behind a sand berm connected by a shallow zig-zag trench. Two M60 machine guns, B-40 rocket-propelled grenades and two DK-82 mortar/grenade launchers were in the firing positions. On the West Beach a heavy machine gun, an M-60, B-40 rocket-propelled grenades and a 75 mm recoilless rifle were dug into connected firing positions. North of each beach was a 60 mm mortar and south of the beaches was an 81 mm mortar that could fire on either beach. Ammunition was stored in dug-in bunkers one behind each beach, with a third ammunition dump located near Em Son's command post in the jungle south of the beaches.[1]:132-133

On their arrival at Rong Sang Lem Captain Miller was taken to the senior Khmer Rouge commander where he was subject to a cursory interrogation before being asked if he could talk to the American planes from the Mayaguez. The Khmer Rouge explained that they had already lost three boats and numerous men and were obviously anxious to call off the American bombers. Captain Miller explained that if they returned to the ship and restarted its engines they could then generate electricity to call their office in Bangkok which could then contact the U.S. military. The Khmer Rouge radioed instructions to their higher command and then gave approval for Captain Miller and nine men to return to the Mayaguez. As darkness was falling it was decided that they would return to the Mayaguez the following morning, 15 May.[1]:114-118

At 06:13 on May 15, the first phase of the operation began with the transfer by three HH-53s of D/1/4 Marines to the Holt. As the Holt slowly came alongside, USAF A-7D aircraft saturated the Mayaguez with tear gas munitions. Equipped with gas masks, the Marines at 07:25 hours then conducted one of the few hostile ship-to-ship boardings by the U.S. Navy since the American Civil War, securing the vessel after an hour-long search, finding it empty.[1]:185-188

USS Harold E. Holt pulls alongside the SS Mayaguez to allow the boarding party to board

At 06:12, the eight helicopters (five CH-53 Knifes and three HH-53 Jolly Greens) of the Koh Tang assault force approached the two Landing zones (LZs) on Koh Tang. At the West Beach, the first section of two CH-53 helicopters came in at 06:20 hours. The first helicopter; Knife 21, landed safely, but while offloading its Marines came under heavy automatic weapons fire, destroying an engine. It managed to take off, protected by suppressive fire from the second CH-53, Knife 22, and ditched 1.6 km offshore. Knife 22 was damaged so severely that it turned back with its Marines (including the Golf Company commander) still aboard escorted by Jolly Green 11 and Jolly Green 12, and crash-landed in Trat Province on the Thai coast, where its passengers were picked up by Jolly Green 12 and returned to U-Tapao.[4]:248[1]:159-162, 209-210

At 06:30, the CH-53s approaching the East Beach encountered intense automatic weapons and RPG fire from entrenched Khmer Rouge. Knife 31 was hit by two RPGs, which ignited its left fuel tank and ripped away the nose of the helicopter. It crashed in a fireball fifty meters offshore. A pilot, five Marines, and two Navy corpsmen were killed in the crash, another Marine drowned swimming from the wreck, and three Marines were killed by gunfire trying to reach the beach. A tenth Marine died of his wounds while clinging to the burning wreckage. The surviving ten Marines and three Air Force crewmen were forced to swim for two hours before being picked up by the gig of the arriving Henry B. Wilson.[1]:195-197 Among the Marine survivors was the battalion's Forward Air Controller, who used an Air Force survival radio while swimming to direct A-7 air strikes against the island until the battery failed. The second CH-53, Knife 23 was hit by an RPG which blew off the tail section and crash-landed on the East Beach, but it successfully offloaded its 20 Marines and crew of five. They set up a defensive perimeter and the Knife 23 copilot used his survival radio to call in airstrikes, but they would remain cut off from both reinforcements and rescue for twelve hours.[4]:248-249[1]:162-167

Knife 32 was inbound to the East Beach when it was hit by an RPG and aborted its landing, instead heading out over the West Beach to the Knife 21 crash site where it dumped fuel and proceeded to rescue the three Knife 21 crewmen.[1]:170-171 Two other sections of the first wave, consisting of the remaining four helicopters, were diverted from the East Beach to the West Beach and eventually landed all of their Marines between 06:30 and 07:00 hours, although the final insertion by Jolly Green 41 required support from an AC-130 Spectre gunship in order to penetrate the Khmer Rouge fire on its fifth attempt. Knife 32, Jolly Green 41 and Jolly Green 42 eventually landed 81 Marines on the West Beach under the command of the company Executive Officer, and Jolly Green 43 landed 29 Marines of the battalion command post and mortar platoon a kilometer to the southwest.[4]:250 By 07:00 109 Marines and five Air Force crewmen were on Koh Tang, but in three isolated beach areas and in close contact with Khmer Rouge troops. The Marines at the northern end of West Beach attempted to move down the beach to link up with Col Austin's command element to the south, but was beaten back by heavy Khmer Rouge fire which killed LCPL Ashton Loney.[1]:176-178 While isolated, the Marines were able to use their 81 mm mortars as fire support for their contingents and devised a makeshift communications network for controlling supporting air strikes by USAF A-7 and F-4 aircraft. It was decided that the platoon isolated on the East Beach should be extracted and following suppressive fire from an AC-130, Jolly Green 13 landed there at 08:15 amid a hail of machine gun fire, but it had landed some 100 m away from the Marines who were reluctant to risk running to the helicopter, and Jolly Green 13 took off with its fuel lines ruptured and made an emergency landing in Rayong, Thailand.[4]:249-251[1]:175-176

Of the eight helicopters assaulting Koh Tang, three had been destroyed (Knife 21, Knife 23 and Knife 31) and four others damaged too severely to continue operations (Knife 22, Knife 32, Jolly Green 41 and Jolly Green 42) and of the helicopters used in the Mayaguez recapture Jolly Green 13 had been severely damaged in the East Beach rescue attempt.[4]:249-251 This left only three helicopters (all HH-53s - Jolly Greens 11, 12 and 43) of the original eleven available to bring in the follow-up forces of BLT 2/9, so the 2 CH-53s (Knife 51 and 52) whose mission had been search and rescue — the last available helicopters — were reassigned to carry troops.[4]:251 The five helicopters picked up 127 Marines of the second wave at U-Tapao between 09:00 and 10:00 hours.[1]:211-212 At 11:50 Knife 52, Knife 51 and Jolly Green 43 arrived over Koh Tang and prepared to land on the East Beach, as Knife 52 approached fire punctured its fuel tanks and the pilot aborted the landing and headed back to U-Tapao leaking fuel. Knife 51 and Jolly Green 43 also abandoned their landings and assumed a holding pattern.[1]:213-214

U.S. Marines abandon their damaged helicopter Knife 22 in Thailand

East Beach with Knife 23 at left, Knife 31 at right and a destroyed Khmer Rouge Swift Boat

East Beach with Knife 23 top and Knife 31 bottom

Knife 22 after emergency landing in Trat Province, Thailand

BLT 2/9 Command group disembarks Jolly Green 43 on the West Beach

Former Knife 22, number 68-10928, upgraded to MH-53M Pave Low on display at Memorial Air Park, Hurlburt Field, Florida

At 06:07 the Khmer Rouge information and propaganda minister, Hu Nim, made a radio broadcast announcing that the Mayaguez and its crew would be released. The section of his communique on the release was:

Regarding the Mayaguez ship. We have no intention of detaining it permanently and we have no desire to stage provocations. We only wanted to know the reason for its coming and to warn it against violating our waters again. This is why our coast guard seized this ship. Their goal was to examine it, question it and make a report to higher authorities who would then report to the Royal Government so that the Royal Government could itself decide to order it to withdraw from Cambodia's territorial waters and warn it against conducting further espionage and protractive activities. This applies to this Mayaguez ship and to any other vessels like the ship flying Panama flags that we released on May 7, 1975.[2]:162-166

The transmission was intercepted by the CIA station in Bangkok, translated and delivered to the White House by 07:15 (20:15 EDT).[1]:189-190 The White House was skeptical of the Khmer Rouge message and released a press statement at 08:15 (21:15 EDT) saying that U.S. military operations would continue until the crew of the Mayaguez was released. Secretary Kissinger had of his own accord ordered a delay to an airstrike by planes from the Coral Sea on the Kompong Som oil storage complex and Ream airfield.[1]:190-193 At 06:30 on Koh Rong Sanloem the crew of the Mayaguez were informed that they would be allowed to return to their ship, after having first agreed to a statement that they had not been mistreated.[1]:179-183 At 07:15 the Mayaguez crew was loaded aboard the Thai fishing boat, the Sinvari (which had itself been captured by the Khmer Rouge five months earlier) escorted by a second boat with Sa Mean and other Khmer Rouge. Once away from Koh Rong Sanloem the second boat picked up the Khmer Rouge guards from the Sinvari and instructed the crew to return to the Mayaguez and call off the American planes.[1]:197-199 At 09:35 an orbiting P-3 Orion spotted the Sinvari and the Wilson was ordered to intercept her, originally thinking it was a Khmer Rouge gunboat. The P-3 then identified that Caucasians were aboard and at 09:49 the Mayaguez crew was brought aboard the Wilson. Confirmation of the release of the crew was sent to the White House and at 11:27 (00:27 EDT) President Ford went on U.S. national television announcing the recovery of the Mayaguez and the rescue of its crew, but obscuring the fact that the crew had in fact been released by the Khmer Rouge.[1]:199-201[1]:204-207

President Ford, at Secretary Kissinger's urging, declined to cancel the scheduled airstrikes on the Cambodian mainland until the Marines on Koh Tang had been withdrawn.[1]:206 At 09:05 A-6A and A-7E aircraft from VA-22, VA-94 and VA-95 escorted by F-4N fighters of VF-51 and VF-111 aboard the Coral Sea had begun the delayed airstrikes, bombing landing barges and oil storage facilities at Kompong Som and cargo planes and T-28 Trojan aircraft at Ream airfield and boats at Ream naval base.[1]:193

The U.S. Joint Chiefs of Staff decided that, with the ship recaptured and the crew released, further reinforcement of Koh Tang was unnecessary and at 11:55 they ordered the U.S. forces to "immediately cease all offensive operations against the Khmer Republic [and to] disengage and withdraw all forces from operating areas as soon as possible". Hearing this order, the orbiting EC-130 Cricket recalled the second assault wave. The helicopters with the second wave reversed course until Lt. Col. Austin, on the ground on Koh Tang, convinced the commander of the Seventh Air Force that the reinforcements were necessary to prevent his units from being overrun; the order was rescinded at 12:10.[1]:214-215

The second wave carrying the Marines from Knife 22 and a platoon from Company E had originally taken off at staggered times between 09:00 and 10:00, but with the reversal of course its arrival on Koh Tang was seriously delayed.[4]:252 At 12:10 Knife 51, followed by Jolly Greens 43, 11 and 12 successfully landed 100 additional Marines and evacuated nine wounded on the West Beach, making a total of 225 Marines - 205 on the West Beach and 20 Marines and five Airmen on the East Beach.[4]:257 Around the same time Lt. Col Austin's isolated command unit planned a linkup of its small contingent with the bulk of Golf Company at the northern end of the West Beach. Using mortar fire and A-7 airstrikes to clear Khmer Rouge in the jungle between the two forces, it reached the Golf Company perimeter at 12:45.[1]:215-217

By 14:00 firing on the West Beach had reduced substantially as Em Son had moved most of his men back from the beaches with only three man patrols maintaining pressure on the two Marine enclaves. Lt. Col Austin asked the Cricket if he should attempt to push across the island to link up with the isolated unit on the East Beach, but was advised that another helicopter pickup would be attempted first.[1]:218-224 At 14:15 Jolly Greens 11 and 43 approached East Beach, but were repulsed by heavy fire. Jolly Green 43 had a fuel line damaged, but made an emergency landing on the Coral Sea at 14:36, where it was repaired and returned to service by 17:00 hours.[4]:258 During the attempted landing by Jolly Green 43, fire was seen coming from a semi-submerged Swift Boat that had been shot up by an AC-130 the previous day, A-7 aircraft were called in to destroy the boat with their 20 mm cannon.[1]:225-226 At 16:20 hours, Nail 68, an Air Force OV-10Forward air control (FAC) aircraft, arrived and took over the direction of air support. At 16:23 Nail 68 called on the Wilson to use its 5 inch gun to destroy the semi-submerged Swift Boat.[1]:228 This change in controllers marked a turning point in the quality of airborne firepower available to the Marines, because for the first time that day they had an airborne observer exclusively dedicated to providing accurate and timely close air support.[4]:257 At 17:00 Em Son gathered his forces and moved back up the island to secure an ammunition dump that lay between the West and East Beaches. He was surprised to find the dump intact and no Marines lying in ambush. Now resupplied, his men would be able to increase the pressure on the Marines again.[1]:229-231

At 18:00 as the sun began setting a third attempt to rescue the East Beach force was attempted, using Jolly Green 11 as the rescue ship and with gunfire support from Jolly Green 12, Knife 51 and the gig from the Wilson mounting four M-60s. Nail 68 first ordered gun runs by an AC-130 followed by F-4s and A-7s along the edge of the East Beach, as this was going on five C-130s arrived over Koh Tang carrying BLU-82 "daisy cutter" bombs — a 15,000-pound device and the largest conventional explosive weapon in the U.S. arsenal at the time. Not seeing any practical use for the BLU-82s, Nail 68 ordered them dropped well south of the Marines' positions. At 18:15 Jolly Green 11 approached the East Beach, but did not actually set down because the hulk of Knife 23 was sitting on the beach; instead, the pilot (1LT Donald Backlund) skilfully hovered the helicopter several feet off the ground just north of the original beach LZ. The extraction was difficult because the helicopter would see-saw up and down. Only a few Marines at a time could board the helicopter's rear ramp in this fashion by timing their jumps to coincide with the downward motion of the aircraft. Jolly Green 11 was hit numerous times, but managed to transport its cargo of 20 Marines and five Airmen to the Coral Sea.[4]:258 Shortly after Jolly Green 11 evacuated the East Beach, the first BLU-82 was dropped causing a huge explosion and sending a shockwave across the West Beach, Lt. Col Austin quickly called the Cricket with the instruction that no more of the bombs should be dropped.[1]:231-235 A report from Jolly Green 11 indicated that a Marine might be in the wreckage of Knife 31 and Jolly Green 12 went in to search for any survivors, Jolly Green 12 hovered above the wreck, while a crewman was lowered on a rescue hoist to survey the wreckage, no Marine was recovered and Jolly Green 12 suffered extensive damage in the rescue attempt and flew to the Coral Sea.[4]:259[1]:235

As a moonless night fell over Koh Tang, the remaining two helicopters, Knife 51 and the hastily repaired Jolly Green 43, were joined by Jolly Green 44 that had been out of service at its Nakhon Phanom base but had been repaired and flown to the area. At 18:40 this force began to withdraw the remaining 205 Marines from the West Beach, protected by AC-130 fire and naval gunfire support from the Henry B. Wilson and its gig. The first load of 41 Marines was lifted out at 18:40 hours by Knife 51 and flown to the Coral Sea, followed by 54 taken aboard Jolly Green 43. As Jolly Green 44 picked up a load of 44 Marines, the remaining Marines in the shrinking West Beach perimeter came under intense attack and were in danger of being overrun. The trip to the Coral Sea was a thirty-minute round trip, so the pilot (1LT Bob Blough) decided to deliver his Marines to the Harold E. Holt, the nearest ship to Koh Tang, made in complete darkness while hovering over the ship with only its front wheels touching down. Within five minutes Jolly Green 44 returned and picked up 34 more Marines, leaving 32 still on the island, Jolly Green 44 was suffering engine trouble and this time headed for the Coral Sea.[1]:238-243

Finally at 20:00 Knife 51 landed and began loading in the dark and under fire. Having loaded everyone save for themselves, Captain Davis and Gunnery Sergeant McNemar combed the beach looking for stragglers. Knife 51 Pararescueman TSGT Wayne Fisk was at the end of the ramp when two more Marines stumbled out of the darkness, TSGT Fisk asked Captain Davis if all his men were aboard and he confirmed they were, but TSGT Fisk combed the beach one last time for stragglers, finding none, he leaped onto the hovering CH-53 and at 20:10 Knife 51 left Koh Tang for the Coral Sea.[4]:262[1]:243-248

Due to the intense direct and indirect fire during the operation, the bodies of Marines and airmen who were killed in action were left where they fell including Lance Corporal Ashton Loney, whose body was left behind in the darkness during the evacuation of the West Beach.[1]:238-240

With each withdrawal, the Marines contracted their perimeter on the West Beach. Lance Corporal John S. Standfast, squad leader, 3rd Squad, 3rd Platoon, Company E and his squad covered Company G's withdrawal during the reduction of the perimeter, and he then singlehandedly directed the pullback of his own squad. Before withdrawing to the safety of the new perimeter, Standfast and his platoon guide, Sergeant Andersen would move forward to the old perimeter to ensure that no member of the company inadvertently had been left behind, each time checking every foxhole. As the Company E commander, Captain Mykle E. Stahl, prepared to board Jolly Green 44 he informed Captain Davis that all of his men were inside the perimeter, not realising that three Marines of an M60 machine gun team had set up a firing position behind a rocky outcrop beyond the right flank of the perimeter.[4]:262[1]:239-240

Even as Knife 51 left the West Beach, there was confusion as to whether any Marines remained on Koh Tang, the pilot Lieutenant Brims radioed the FAC that some Marines aboard claimed there were still fellow Marines on the ground, but this was soon contradicted by Captain Davis who said that all Marines were off Koh Tang.[1]:248 Two hours after the evacuation was completed, with the Koh Tang Marines dispersed among three Navy ships, the Company E commander, Captain Stahl, discovered that three of his Marines were missing. The Marines checked all of the Navy ships, but could not locate Lance Corporal Joseph N. Hargrove, PFC Gary L. Hall, and Pvt Danny G. Marshall, members of a three-man machine gun team which had been assigned to protect the right flank of the constantly shrinking perimeter during the final evacuation.[1]:254 Sergeant Andersen was the last member of the Marine force to see Hall, Hargrove, and Marshall alive at about 20:00 when he ordered them to move back to a new position which was located to the left of the position occupied by Captain Davis.[4]:263[1]:239

A rescue operation was proposed using Marine volunteers aboard the only three serviceable helicopters. On the Coral Sea the Commander of Task Force 73, Rear Admiral R. T. Coogan met with Lt. Col Austin and Captain Davis, Gunnery Sergeant McNemar and Lieutenant Coulter who had just arrived from Subic Bay with a 14-man U.S. Navy SEAL team to consider possible options. Admiral Coogan asked Lt. Coulter to take the Wilson gig ashore in daylight unarmed under a white flag with leaflets dropped and the Wilson broadcasting the crew's intentions to recover the American bodies and determine the status of the missing men if possible, but Lt. Coulter was skeptical and instead proposed taking his team ashore for a night reconnaissance, but this was refused by Admiral Coogan. Admiral Coogan had to weigh up the order from Seventh Fleet to cease hostile actions against the Khmer Rouge against the lack of evidence that any of the men were still alive, he decided that there would be no rescue mission unless there was some confirmation that the three Marines were still alive.[1]:254-255 The following morning the Wilson cruised back and forth between the West and East Beaches for three hours broadcasting messages in English, French and Khmer saying that they had no hostile intent, but simply wished to retrieve any U.S. personnel dead or alive on the Koh Tang and would send an unarmed boat ashore if the Khmer Rouge signalled them. Half of the Wilson crew was on deck scanning the beaches and jungle for any sign of the missing Marines, but no signal was received from the Khmer Rouge or the missing Marines. With no indication that the three Marines were still alive and the certainty that more lives would be lost in any forced rescue attempt, a return to Koh Tang was ruled out and the Wilson departed the area.[1]:255-256 Hargrove, Hall, and Marshall were declared Missing in Action and then on 21 July 1976 their status was changed to Killed in Action (Body Not Recovered).[1]:265-266

In 1985, an eyewitness report indicated that a wounded American had been captured on Koh Tang after the assault and was subsequently executed.[1]:16 In 1999 Em Son approached the Joint Task Force-Full Accounting (JTF-FA) on learning that they were looking for further information regarding the events on Koh Tang.[1]:277 Em Son advised that on the morning on 16 May he ordered his men to search the West Beach for any remaining Americans. About 100 m from the beach one of the Khmer Rouge was hit by M-16 fire, the Khmer Rouge then fired mortars and encircled the firing position capturing one American with a leg wound, Em Son's description of the American matched that of Lance Corporal Joseph Hargrove. The Khmer Rouge continued their search and located an abandoned M-60 machine gun, various equipment and the covered body of a black American soldier. Em Son ordered the dead American (presumably Lance Corporal Ashton Loney) buried and the prisoner taken to his H.Q., when Em Son was advised that the Khmer Rouge hit by M-16 fire had died, he ordered the American to be shot.[1]:281-286[5] Approximately one week after the assault, Em Son's men noticed that their leftover food was being disturbed and on searching they found bootprints in the mud, they set up a night ambush and on the third night they captured two Americans matching the descriptions of PFC Gary Hall and Pvt Danny Marshall. Em Son radioed Kampong Som and was ordered to deliver the Americans to the mainland. The following morning the two Americans were taken by boat to the mainland and then driven to the Ti Nean Pagoda above Sihanoukville where they were stripped to their underwear and shackled. After one week, on orders from Phnom Penh, each American was beaten to death with a B-40 rocket launcher, the body of Hall was buried in a shallow grave near the beach while that of Marshall was dumped on beach cove[1]:286-289[6]

Recovery efforts in 1999 by the JTF-FA later found bone fragments that might have belonged to Hall and Marshall, but DNA tests proved inconclusive due to the small size of the fragments.[1]:293-297Hargrove, Hall, and Marshall all received Purple Hearts from the U.S. Marine Corps, however, Hargrove's family did not receive the award until 1999, after investigative journalist and author Ralph Wetterhahn published several articles in popular magazines about his findings.[1]:268

In 2007, Hargrove's cousin, Cary Turner, began a campaign to have Joint POW/MIA Accounting Command (JPAC), the successor agency to JTF-FA, return to Koh Tang to search for Hargrove's remains. In October 2008 JPAC, was reported to have found four sets of remains in an area indicated by Em Son as being where the American suspected to be Hargrove was buried. One of the sets of remains was said to be Caucasian in nature, but DNA analysis was needed before the identity could be confirmed.[7]

Between 1991 and 1999, U.S. and Cambodian investigators conducted seven joint investigations, led by the Joint Task Force-Full Accounting. On three occasions Cambodian authorities unilaterally turned over remains believed to be those of American servicemen. In October and November 1995, U.S. and Cambodian specialists conducted an underwater recovery of the Knife 31 crash site where they located numerous remains, personal effects and aircraft debris associated with the loss. The USS Brunswick, a Navy salvage vessel, enabled the specialists to conduct their excavation offshore. In addition to the support provided by the Cambodian government, the Government of Vietnam also interviewed two Vietnamese informants in Ho Chi Minh City who turned over remains that were later positively identified. As a result of these investigations the remains of 2LT Richard Vandegeer, LCPL Gregory S Copenhaver, LCPL Andres Garcia, PFC Lynn Blessing, PFC Walter Boyd, PFC Antonio R Sandoval and PFC Kelton R. Turner were identified.[40][4]:316-324 In 2012 the remains of PFC James Jacques, PFC Richard W Rivenburgh and PFC James Maxwell were identified.[41]

The Mayaguez incident had a direct effect on the political situation in Thailand, as news of the operation reached Bangkok protests began outside the U.S. Embassy.[42] The U-Tapao air base had been used by U.S. rescue forces despite an explicit refusal of permission by the relatively new civilian Thai government[2]:55-60 (after being refused by the Thai government, the US sought and obtained permission from the Thai military to proceed), resulting in considerable anger towards the United States. The Thai government called the act a violation of Thailand's sovereignty and called for the immediate withdrawal of all U.S. forces from U-Tapao.[1]:256

Some congressmen were dissatisfied with the level of consultation they received under the War Powers Resolution. Senator Mike Mansfield was the most critical, saying "we were informed, not consulted". Senator Thomas Eagleton introduced an amendment to the War Powers Resolution that added the rescue of nationals to the list situations not requiring prior approval by Congress, but also stipulating that only minimum force would be used in rescue.[2]:46,60-63,72-73,168-170

Some crew members brought lawsuits in admiralty law at the San Francisco Superior Court against Sea-Land Service Inc relating to the incident. The crew members claimed that the defendant's Master was derelict in his duty by "recklessly venturing into known dangerous and hostile waters of foreign sovereignty (Cambodia)" inviting the capture. Evidence was provided that Mayaguez was not flying a flag, and had sailed about two nautical miles off Poulo Wai. In June 1977, a settlement was agreed. In February 1979 another settlement was reached by other crew members, making a total settlement of $388,000 to the crew members taking legal action.[3]

The U.S. military received much criticism for its handling of the incident.[43] In addition to the failure of intelligence to determine the whereabouts of the crew of the Mayaguez and the presence of a sizable hostile force on Koh Tang, the timing of the operation was questioned until it became clear that combat had been underway four hours before the crew was released. Within the services, the Marines in particular were critical of the ad hoc nature of the joint operation and the perceived pressure from the Administration for hasty action,[44] although the success of Operation Frequent Wind had been the basis for many decisions made during the crisis. Vice Admiral George P. Steele, the Seventh Fleet commander, later stated that: "The sad part of the Mayaguez is that we had sufficient force coming up with the Seventh Fleet, after it had been turned around from the evacuation of Vietnam stand down, to seize Southern Cambodia. I begged for another day or two, rather than commit forces piecemeal as we did .... The idea that we could use U.S. Air Force air police and Air Force helicopters as an assault force appears to me as ridiculous today as it did then."[4]:239

When many of the coordination and communications problems arose again during Operation Eagle Claw, the hostage rescue mission in Iran in 1980, significant changes in joint and special operations were brought about.[1]:313

In 1996 the Mayaguez-Marine Corps Memorial was dedicated in the grounds of the U.S. Embassy in Phnom Penh by then Ambassador Kenneth M. Quinn and Senator John McCain, the memorial lists the names of the 18 U.S servicemembers killed and missing at Koh Tang and Marine Security Guard Sergeant Charles “Wayne” Turberville killed in a Khmer Rouge grenade attack on 26 September 1971.[45]